This chapter discusses two concepts of compatibility of a hypothesis with the evidence, associated with different concepts of confirmation of hypotheses. It also discusses the matter by analyzing two arguments advanced in the recent symposium on simplicity of hypotheses by Nelson Goodman and by Stephen Barker. The pragmatic concept, like the logical, is in terms of potential falsifiers, but while to determine the class of potential falsifiers in the latter case we need only the rules of language and logic, in the former case we have to know the rules of behavior of the experimenter testing the hypothesis in question, viz. when he is ready to reject the hypothesis. As corroboration in Popper's methodology is restricted to certain test statements, satisfying certain pragmatical conditions, compatibility with evidence is relevant only if it is compatible with the results of severe tests and not with any observation statements.